 Whereas Dixieland and swing tunes might have one chord change every two bars with some sections with one chord change per bar, bebop tunes often had two chord changes per bar with many changing key every four bars.In addition, since bebop was written for listening rather than dancing, the tempo was not constrained by danceability; bebop tunes were often faster than those of the swing era.With bebop's complex tunes and chords and fast tempo, melodic embellishments and playing by ear were no longer sufficient to enable performers to improvise effectively.